When my car was last dynoed back around Aug-Sep of last year I had Predator(custom tune), K&N Cai, and TB Bypass. She put down these numbers:

288 hp
316 tq

To me the hp was kinda on the low side but it was kinda hot/humid that day so I wasn't to worried. I added Borla CB and had them installed last January. I didn't have her dynoed but she showed improvement at the track.

I ordered Kooks Stepped Headers/Mid-pipes from Maryland Speed and had them installed today. Afterwards they did a few dyno pulls and here's what they got:

293 hp
306 hp

When they handed me the dyno sheet I nearly fell out. It definitely was hot/humid today but c'mon I only gained 5 hp and actually lost 10 lb/ft of torque with the addition of full exhaust!!!

Makes me wonder if I should've just got the regular Kooks 1 3/4 instead of paying extra for Kooks SS. Don't get me wrong she sounds lovely with the LT's but the untuned numbers are disapointing!! I still recommend Kooks Stepped Headers. They are a great design but my car didn't respond well to them.

After a few months when it cools down I'll see what the dynojet comes up with. I'll probably have to get a "dyno" tune to get the most out of her but I expected to get better results even untuned.

 

My car responded negatively right after the kooks were installed (321/315) but after the tune I came out at 369/353. I don't have a true baseline but most cts-v's pull around 330/330 on a mustang.

So...why didn't you get it tuned? Do you have a graph? What happened to your AFR? I'd suspect it's too rich.

 

The stepped are a little much for what you have and being untuned isn't helping you at all. Also maybe you have some issues that you don't realize? Do you have an SES light?

Jon

 

Miley is following me everywhere I go...

 

Yeah it is running real rich. On top of that the GTO suffers badly from heat soak and it was very hot today so I suspect I was robbed 10-20 hp from the IAT sensor pulling timing. When it gets cooler in a few months I'll see what she puts down. She sounds lovely though. That Borla/Kook combination is higgly recommended.

 

there is nothing to be dissapointed about. The car is untuned, you always do a tune after installing headers. So your obviously losing your power right there. are those headers stepped to 2 inches or 1 7/8?

 

"the untuned numbers are disapointing!!"

Like everyone else has said you need a tune.

 

Kooks PT# 6700-KR- Signature Series Stepped Header


Here is a list of changes over standard Kooks headers-

1 3/4"-1 7/8" Stepped Primaries

Unique Stamped Merge Collector - Less aggressive merge than competition to not disrupt exhaust flow

2 front and 1 rear O2 sensor extensions (no need for separate 2004 and 2005/06 PT#'s)

Extra O2 bung for a wideband etc. welded on driver side (includes cap)*

Special Signature series primary badge with Kooks signature*

Works with all current Kooks 04-06 Mid pipes

 

Sounds like an 04 GTO. The first #'s are totally normal. 2nd # is probly a lack of a real tune with a ton of heat soak from the crappy GTO inlet system.

 

Yeah it's LS1 GTO A4. I posted this in a GTO forum first. How much do you hp do you think heat soak robbed me?? It was 90+ degree's by time they dynoed it. Some people say 10-15 hp.